Oxidation of crocein orange G by lignin peroxidase isoenzymes

The ligninolytic enzyme system ofPhanerochaete chrysosporiun is able to decolorize several recalcitrant dyes. Three lignin peroxidase isoenzymes, LiP 3.85, LiP 4.15, and LiP 4.65, were purified by preparative isoelectric focusing from the carbon-limited culture medium ofP. chrysosporium. Based on amino terminal sequences, the purified isoenzymes correspond to the isoenzymes H8, H6, and H2, respectively, from theN-limited culture. The purified isoenzymes were used for decolorization of an azo dye, Crocein Orange G (COG). According to the kinetic data obtained, the oxidation of COG by lignin peroxidase appeared to follow Michaelis-Menten kinetics. Kinetic parameters for each isoenzyme were determined. The inactivating effect of ascending H₂O₂ concentrations on COG oxidation is shown to be exponential within the used concentration range. The best degree of decolorization of 100 μM COG was obtained when the H₂O₂ concentration was 150 μM. This was also the lowest H₂O₂ concentration for maximal decolorization of 100 μM COG, regardless of the amount of lignin peroxidase used in the reaction.